The invention relates to a gas generator, particularly for an airbag, having a cylindrical outer tube, the open front ends of which are sealed by cover elements, an inner tube of smaller diameter which is arranged coaxially inside the outer tube and has discharge apertures, an ignitable gas producing material inside the inner tube, filter elements in the annular chamber between the inner and outer tubes, and an ignition unit to ignite the gas producing material.
A gas generator of this kind is known from DE 43 24 554 A1 for example. This known gas generator has a cylindrical outer tube which represents the housing of the gas generator and the open front ends of which are sealed by cover elements. A cylindrical inner tube of smaller diameter is coaxially arranged in the outer tube; this internal tube defines the limits of the combustion chamber, in which a gas-producing material which can be ignited by means of an ignition unit is accommodated, and is provided with several discharge apertures in the tube wall. In the annular chamber between the inner and the outer tubes is a filter element which generally comprises a multiplicity of layers of wire mesh, steel wool and/or metal fibre fleece. The combustion gas which emerges from the discharge apertures of the inner tube flows through the filter elements which absorb solid and liquid and/or condensed combustion products and escapes, cleaned, via gas outlet apertures in the outer tube.
In order to obtain constant aperture gas pressures at all temperatures, a rolled, self-overlapping insulating strip which at least partially lies against the wall is arranged in the inside of the inner tube in order to insulate the discharge apertures.
On the outside of the inner tube the discharge apertures are covered with a sealing strip to seal against moisture.
A gas generator in which the gas-generating material is arranged in a charge container made of a metal foil is known from U.S. Pat. No. 4,131,299. This has the advantage that an additional insulating strip and sealing strip can be dispensed with. Furthermore, the assembly of the gas generator is substantially simplified as the charge container can be filled away from the actual production line and further processed in the sealed condition. This substantially increases safety.
A gas generator arrangement with a flame guide tube is known from DE 43 93 229 T1. This tube extends in the axial direction of the housing and a multiplicity of apertures are formed in the side wall of the flame guide tube. The outside of the flame guide tube thus defines the flame guiding. Furthermore, intensifier charges are accommodated in the flame guide tube. The shock wave or flame from the ignition charge and/or intensifier charge moves through the flame guide tube and finds its way through the apertures into the gas-generating charge and ignites it. The number and position of the apertures is selected in such a way that the gas-generating charge is "over-ignited". This means that the gas-generating charge is ignited at a multiplicity of different places in order to ensure that the pressure of the generated gas exhibits no undesirable pressure peaks, so as to ensure controlled burning.